Multiple prompts in a single screen, logical, labeled, or repeated groups of prompts

ODK Collect does not recompute the relevance (visibility) of all the questions on a screen as data is entered into those questions. As a result, if you have Q2 relevance (visibility) depending upon an answer to Q1, and both are on the same screen, Q2 will be visible or hidden based upon the initial state of Q1 when the combined screen is shown, and it will never display until you leave and re-enter the screen, at which point the value of Q1 will be re-examined and Q2 will be made visible based upon Q1's (now potentially different) value.